Quality of Service In Data Networks

1
Quality of Service In Data Networks

• Raj JainThe Ohio State UniversityColumbus, OH
  43210Jain_at_cse.ohio-State.Edu
• These slides are available on-line
  athttp//www.cse.ohio-state.edu/jain/cis788-99/

2
Overview

• ATM QoS and Issues
• Integrated services/RSVP and Issues
• Differentiated Services and Issues
• QoS using MPLS
• End-to-end QoS

3
QoS Components
Signaling and Admission control
1
Policing
3
Shaping
2
Scheduling
5
Routing
4
Buffer Mgmt
6
7
Traffic Monitoring and feedback
4
ATM QoS
Today
ATM

• Too much too soon

5
ATM QoS Issues

• Cant easily specify QoS What is the CDV
  required for a movie?
• Signaling too complex Þ Need Lightweight
  Signaling
• Need priority or weight among VCs to map DiffServ
  and 802.1D
• Need Group Address
• Need Heterogeneous Point-to-Multipoint
  Variegated VCs
• Cant easily aggregate QoS VP S VCs
• Need QoS Renegotiation

6
Integrated Services

• 1. Best Effort Service Like UBR.
• 2. Controlled-Load Service Performance as good
  as in an unloaded datagram network. No
  quantitative assurances. Like nrt-VBR or UBR w
  MCR
• 3. Guaranteed Service rt-VBR
• Firm bound on data throughput and delay.
• Like CBR or rt-VBR
• Need a signaling protocol RSVP
• Design philosophy similar to ATM
• Per-flow
• End-to-end
• Signaling

7
Before Marriage
8
After Marriage
9
Problems with IntServRSVP

• Complexity in routers classification, scheduling
• Not scalable with of flowsÞ Not suitable for
  backbone.
• Need a concept of Virtual Paths or aggregated
  flow groups for the backbone.
• Need policy controls Who can make reservations?
  Þ RSVP admission policy (rap) working group.
• Receiver Based Need sender control/notifications
  in some cases.
• Soft State Need route/path pinning (stability).
• No negotiation and backtracking
• Note RSVP is being revived for MPLS and DiffServ

10
Trend Differentiation Not Integration
d/dx
Þ

• DiffServ to standardize IPv4 ToS bytes first six
  bits
• Packets gets marked at network ingressMarking Þ
  treatment (behavior) in rest of the netSix bits
  Þ 64 different per-hop behaviors (PHB)

11
DiffServ (Cont)

• Per-hop behavior of link bandwidth, Priority
• Services End-to-end. Voice, Video, ...
• Transport Delivery, Express Delivery,...Best
  effort, controlled load, guaranteed service
• DS group will not develop servicesThey will
  standardize Per-Hop Behaviors
• Marking based on static Service Level
  Agreements (SLAs). Avoid signaling.

12
Expedited Forwarding

• Also known as Premium Service
• Virtual leased line
• Similar to CBR
• Guaranteed minimum service rate
• Policed Arrival rate lt Minimum Service Rate
• Not affected by other data PHBs Þ Highest data
  priority (if priority queueing)
• Code point 101 110

13
Assured Forwarding

• PHB Group
• Four Classes No particular ordering
• Three drop preference per class

14
Assured Forwarding (Cont)

• DS nodes SHOULD implement all 4 classes and MUST
  accept all 3 drop preferences. Can implement 2
  drop preferences.
• Similar to nrt-VBR/ABR/GFR
• Code Points

• Avoids 11x000 (used for network control)

15
Problems with DiffServ

• End-to-end ? S per-HopDesigning end-to-end
  services with weighted guarantees at individual
  hops is difficult.Only Expedited Forwarding will
  work.
• Designed for static Service Level Agreements
  (SLAs)Both the network topology and traffic are
  highly dynamic.
• How to ensure resource availability inside the
  network?
• DiffServ is unidirectional Þ No receiver control

16
DiffServ Problems (Cont)

• QoS is for the aggregate not micro-flows.Not
  intended/useful for end users. Only ISPs.
• Large number of short flows are better handled by
  aggregates.
• Long flows (voice and video sessions) need
  per-flow guarantees.
• High-bandwidth flows (1 Mbps video) need per-flow
  guarantees.
• Þ DiffServ alone is not sufficient for
  backbone.Signaling via RSVP will be required.

17
MPLS Mechanisms for QoS

• Explicit Routing Multiple label switched paths
  (LSPs) can be used in parallel to the same
  egress.
• Signaling, Admission Control, Routing Each LSP
  can have priority, preemption, policing,
  overbooking
• Constrained based routing of LSPsAllows both
  Traffic constraints and Resource Constraints
  (Resource Attributes)
• Hierarchical division of the problem (Label
  Stacks)
• Danger Too much too soonagain

18
Bandwidth Broker

• Repository of policy database. Includes
  authentication
• Users request bandwidth from BB
• BB sends authorizations to leaf/border
  routersTells what to mark.
• Ideally, need to account for bandwidth usage
  along the path
• BB allocates only boundary or bottleneck

H
H
H
DMZ
R
BR
R
BR
BB
R
R
19
IEEE 802.1D Model

• Massive bandwidth. Simple priorities will do.
• Up to eight priorities Strict.
• 1 Background
• 2 Spare
• 0 Best Effort
• 3 Excellent Effort
• 4 Control load
• 5 Video (Less than 100 ms latency and jitter)
• 6 Voice (Less than 10 ms latency and jitter)
• 7 Network Control

20
End-to-end View

• ATM/PPP backbone, Switched LANs/PPP in Stub
• IntServ/RSVP, 802.1D, MPLS in Stub networks
• DiffServ, ATM, MPLS in the core

Switched LANs/PPP
ATM/PPP
Switched LANs/PPP
IntServ/RSVP,802.1D, MPLS
DiffServ, ATM, MPLS
IntServ/RSVP,802.1D, MPLS
COPS
COPS
BB
BB
BB
R
R
R
R
R
R
R
R
R
Edge
Edge
Core
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Additional Mechanisms

• Policy based Routing
• Weighted Fair Queueing
• Weighted Random Early Detection
• Link Fragmentation and Interleaving
• These internal mechanisms do not require
  standardization

22
Summary

• ATM CBR, VBR, ABR, UBR, GFR
• Integrated Services GS rtVBR, CLS nrt-VBR
• Signaling protocol RSVP
• Differentiated Services will use the DS byte
• MPLS allows traffic engineering and is most
  promising
• 802.1D allows priority

23
References

• For a detailed list of references see
  refs/ipqs_ref.htm
• Integrated Services Overview, http//www.cse.ohio-
  state.edu/jain/cis788-97/integrated_services/inde
  x.htm
• Multimedia over IP (RSVP, RTP, RTCP, RTSP),
  http//www.cse.ohio-state.edu/jain/cis788-97/ip_m
  ultimedia/index.htm
• Additional papers and presentations on QoS are
  athttp//www.cse.ohio-state.edu/jain/

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Thank You!